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Big Block 284/484 Mopar Performance Purple Shaft - Why all the hate?

ykf7b0

ykf7b0

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I have done lots of web reading recently regarding MP cams and there is a sizeable following that will not recommend the MP 284/484 108 lobe angle camshaft (P4120235). Some even consider it a complete dog. I myself have ran these cams on more than one occasion with much great success and I don't understand the bad feedback. Most will say it can be out-performed with modern grind cams but with a factory iron head engine with no major porting, at least 10.0 to 1 compression, a 3000 rpm stall converter (if automatic), and decent rear gearing (3.55 or shorter) they have been real screamers for me. The drivability has never been an issue at all. I know I am opening a can of worms but I would like to read why these cams get no respect from some folks. Anyone wanting to give it respect should chime in as well.
 
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ykf7b0 said:
I have done lots of web reading recently regarding MP cams and there is a sizeable following that will not recommend the MP 284/484 108 lobe angle camshaft (P4120235). Some even consider it a complete dog. I myself have ran these cams on more than one occasion with much great success and I don't understand the bad feedback. Most will say it can be out-performed with modern grind cams but with a factory iron head engine with no major porting, at least 10.0 to 1 compression, a 3000 rpm stall converter (if automatic), and decent rear gearing (3.55 or shorter) they have been a real screamers for me. The drivability has never been an issue at all. I know I am opening a can of worms but I would like to read why these cams get no respect from some folks. Anyone wanting to give it respect should chime in as well.
Click to expand...
Ran one for years in a mild, home-ported 906, 440, manual trans, 3.91 gears. I liked it. Would have swapped the same can over to another engine if a couple lifters hadn't got mixed up when I switched to a solid.
 
people don't like what they don't understand. the 284-.484 basically is a copy of the racer brown ssh25.
 
I think that cam is just fine. Sure, there are more modern "split lobe" designs. Now, the 292/509 purple cam (80's design) is a little too big for power brakes in my opinion. (whoops, there goes the second can of worms)
 
PurpleBeeper said:
I think that cam is just fine. Sure, there are more modern "split lobe" designs. Now, the 292/509 purple cam (80's design) is a little too big for power brakes in my opinion. (whoops, there goes the second can of worms)
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Hey I have run the 292/.509 cam and had no adverse drive ability or brake issues . lol just playing into your can of worms.
 
For me it has nothing to do with split pattern or single. It has to do with the shape of the lobe, the original intended usage, and the existing quality control.
The lobe was designed in the 60s, with the full and complete knowledge of valvetrain dynamics, head flow, and engine performance. A lot has changed since then, and modern grinds make much better use of the gains uncovered since that time.
When it was designed, you could get high quality high test fuel from the local filling station for under $1. Economy was not a concern. Amenities like power brakes and power steering and AC were options... not standard equipment. Enthusiasts of the day were not looking for well rounded performance. Or call it performance with certain realities included.
The last MP cam I used was about 13 years ago. The quality control was horrid. Varience in lift lobe to lobe, lobe timing cylinder to cylinder, and ICL all were present. It took 8° of keyways to get it where it was advertise. Another 4° to get it where I wanted it. Basically, it was a piece of ****.
I build engines that have to do double, or triple duty. They have to idle in traffic, maybe run AC, maybe run down the strip, maybe run at speed down the highway or a road course. So to get a more usable power curve, with less need for deeper gearing or higher static ratios I'll pay more for a modern grind that's made well.
 
That sucks about the quality.

I ran one in a '70 9.5:1 (advertised) 383 HP with factory converter and 3.55 rear.

It was fine on late 80's/early 90's 89 and 93 octane.

I did degree it as per the MP instructions.

The biggest issue I had was finding a carb that worked. It needed fairly small primaries but a big volume on the secondaries.

Almost everyone I talked to said that it was "too big" a cam for my build, but it worked out great, and I was super happy.
 
I never said they don't work. They do. When made with some semblance of quality, matched with the right parts and machining, and in the rpm range they old manuals say they do. Some things, like torque convertors, have also advanced light years ahead and a modern convertor can certainly help with the issues the MP designs can exasperate. But- there are reasons why a modern performance rebuilt engine makes as much power as it does. A big one of them is modern camshaft design.
 
All things being equal, which cam (s) do you propose would be superior to the 284/484?
 
I had a 484 cam in my 6 bbl GTX for about 10 years, I liked it ok but switched to a Mr. Six Pack cam two years ago.
For me the problem was idle quality in trying to tune the six bbl carbs, not enough vacuum at idle to make them work as they should.
My new cam makes about the same power but moved the curve down low where I want it for a street car, and I have 18 inches of vacuum and my throttle blades are now down into the idle circuit.
Still have the 484 and matched lifters and timing set on a shelf, who knows might use it again.
 
one of the real problems with this cam, and other big hydraulics, is the need for a well tuned ignition. these high overlap hydraulics with tight LSA's need quick curves with 18-20 degrees of initial timing. they don't lend themselves well to cast exhaust manifolds either. if one doesn't understand these principals then they would be better off sticking with a more conservative lobe profile and LSA.
 
I like this cam, with the right combination of other mods, and yes it likes timing.
 
lewtot-RacerBrown, been many many moons ago!!!!!! I also liked the 284 cam but quickly moved past it in years gone by.
 
lewtot-RacerBrown, been many many moons ago!!!!!! I also liked the 284 cam but quickly moved past it in years gone by.
 
oldbee said:
lewtot-RacerBrown, been many many moons ago!!!!!! I also liked the 284 cam but quickly moved past it in years gone by.
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back in the late '60's the racer brown ssh25 was mopars recommended street cam. from what info i have the two cams are identical. mopar tweaked their numbers a little but the 284-.484 i measured had identical numbers to the ssh25. i ran an ssh44 for a short period of time; i believe it to be the basis for the 292-.509.
 
lewtot184 said:
one of the real problems with this cam, and other big hydraulics, is the need for a well tuned ignition. these high overlap hydraulics with tight LSA's need quick curves with 18-20 degrees of initial timing. they don't lend themselves well to cast exhaust manifolds either. if one doesn't understand these principals then they would be better off sticking with a more conservative lobe profile and LSA.
Click to expand...
I agree with it needing lots of timing as my initial timing is at 23 degrees. I set it using a vacuum gauge to find the sweet spot.
 
this cam needs compression and gears. Even then the low end torque is pretty bad.
 
I advanced mine 2 degrees and took care of any torque issues.
 
Mine needed lots of timing IIRC I was close to 30* init!

I never had a problem with low end, although you could feel the power build exponentially through the mid-range.

I had heard good things about the 509 cam but I think that would have been the actual point where I'd have lost the low end in that motor.
 
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